#include "chess.h"

////
//// Includes
#include <algorithm>
#include <cassert>


//#include "history.h"
#include "movegen.h"
#include "movepick.h"
#include "search.h"
#include "thread.h"







////
//// Local definitions
////

namespace {

	enum Stages {
		MAIN_SEARCH, CAPTURES_INIT, GOOD_CAPTURES, KILLERS, COUNTERMOVE, QUIET_INIT, QUIET, BAD_CAPTURES,
		EVASION, EVASIONS_INIT, ALL_EVASIONS,
		PROBCUT, PROBCUT_INIT, PROBCUT_CAPTURES,
		QSEARCH_WITH_CHECKS, QCAPTURES_1_INIT, QCAPTURES_1, QCHECKS,
		QSEARCH_NO_CHECKS, QCAPTURES_2_INIT, QCAPTURES_2,
		QSEARCH_RECAPTURES, QRECAPTURES
	};

	// partial_insertion_sort() sorts moves in descending order up to and including
	// a given limit. The order of moves smaller than the limit is left unspecified.
	void partial_insertion_sort(ExtMove* begin, ExtMove* end, int limit) {

		for (ExtMove *sortedEnd = begin, *p = begin + 1; p < end; ++p)
			if (p->value >= limit)
			{
				ExtMove tmp = *p, *q;
				*p = *++sortedEnd;
				for (q = sortedEnd; q != begin && *(q - 1) < tmp; --q)
					*q = *(q - 1);
				*q = tmp;
			}
	}

	// pick_best() finds the best move in the range (begin, end) and moves it to
	// the front. It's faster than sorting all the moves in advance when there
	// are few moves, e.g., the possible captures.
	Move pick_best(ExtMove* begin, ExtMove* end) {

		std::swap(*begin, *std::max_element(begin, end));
		return *begin;
	}

} // namespace


  /// Constructors of the MovePicker class. As arguments we pass information
  /// to help it to return the (presumably) good moves first, to decide which
  /// moves to return (in the quiescence search, for instance, we only want to
  /// search captures, promotions, and some checks) and how important good move
  /// ordering is at the current node.

  /// MovePicker constructor for the main search
MovePicker::MovePicker(Position& p, Move ttm, Depth d, const ButterflyHistory* mh,
	const CapturePieceToHistory* cph, const PieceToHistory** ch, Move cm, Move* killers_p)
	: pos(p), mainHistory(mh), captureHistory(cph), contHistory(ch), countermove(cm),
	killers{ killers_p[0], killers_p[1] }, depth(d){

	assert(d > DEPTH_ZERO);

	stage = m_have_bit(pos.checkers()) ? EVASION : MAIN_SEARCH;
	ttMove = ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE;
	stage += (ttMove == MOVE_NONE);
}

/// MovePicker constructor for quiescence search
MovePicker::MovePicker(Position& p, Move ttm, Depth d, const ButterflyHistory* mh, const CapturePieceToHistory* cph, Square s)
	: pos(p), mainHistory(mh), captureHistory(cph) {

	assert(d <= DEPTH_ZERO);

	if (pos.in_check())
		stage = EVASION;

	else if (d > DEPTH_QS_NO_CHECKS)
		stage = QSEARCH_WITH_CHECKS;

	else if (d > DEPTH_QS_RECAPTURES)
		stage = QSEARCH_NO_CHECKS;

	else
	{
		stage = QSEARCH_RECAPTURES;
		recaptureSquare = s;
		return;
	}

	ttMove = ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE;
	stage += (ttMove == MOVE_NONE);
}

/// MovePicker constructor for ProbCut: we generate captures with SEE higher
/// than or equal to the given threshold.
MovePicker::MovePicker(Position& p, Move ttm, Value th, const CapturePieceToHistory* cph)
	: pos(p), captureHistory(cph), threshold(th) {

	assert(!pos.in_check());

	stage = PROBCUT;
	ttMove = ttm
		&& pos.pseudo_legal(ttm)
		&& pos.capture(ttm)
		&& pos.see_ge(ttm, threshold) ? ttm : MOVE_NONE;

	stage += (ttMove == MOVE_NONE);
}

/// score() assigns a numerical value to each move in a list, used for sorting.
/// Captures are ordered by Most Valuable Victim (MVV), preferring captures
/// near our home rank. Quiets are ordered using the histories.
template<GenType Type>
void MovePicker::score() {

	static_assert(Type == CAPTURES || Type == QUIETS || Type == EVASIONS, "Wrong type");

	for (auto& m : *this) {
		if (Type == CAPTURES)
			m.value = PieceValueMidgame[pos.piece_on(to_sq(m))]
			- Value(200 * relative_rank(pos.side_to_move(), to_sq(m)));
		
		else if(Type == QUIETS)
			m.value = (*mainHistory)[pos.side_to_move()][from_to(m)]
			+ (*contHistory[0])[pos.moved_piece(m)][to_sq(m)]
			+ (*contHistory[1])[pos.moved_piece(m)][to_sq(m)]
			+ (*contHistory[3])[pos.moved_piece(m)][to_sq(m)];

		else { // Type == EVASIONS
			if (pos.capture(m))
				m.value = PieceValueMidgame[pos.piece_on(to_sq(m))]
				- Value(type_of(pos.moved_piece(m)));
			else
				m.value = (*mainHistory)[pos.side_to_move()][from_to(m)] - (1 << 28);
		}
	}
}

/// next_move() is the most important method of the MovePicker class. It returns
/// a new pseudo legal move every time it is called, until there are no more moves
/// left. It picks the move with the biggest value from a list of generated moves
/// taking care not to return the ttMove if it has already been searched.

Move MovePicker::next_move(bool skipQuiets) {

	Move move;

	switch (stage) {

	case MAIN_SEARCH: case EVASION: case QSEARCH_WITH_CHECKS:
	case QSEARCH_NO_CHECKS: case PROBCUT:
		++stage;
		return ttMove;

	case CAPTURES_INIT:
		endBadCaptures = cur = moves;
		endMoves = generate<CAPTURES>(pos, cur);
		score<CAPTURES>();
		++stage;
		/* fallthrough */

	case GOOD_CAPTURES:
		while (cur < endMoves)
		{
			move = pick_best(cur++, endMoves);
			if (move != ttMove)
			{
				if (pos.see_ge(move, Value(-55 * (cur - 1)->value / 1024)))
					return move;

				// Losing capture, move it to the beginning of the array
				*endBadCaptures++ = move;
			}
		}

		++stage;
		move = killers[0];  // First killer move
		if (move != MOVE_NONE
			&&  move != ttMove
			&&  pos.pseudo_legal(move)
			&& !pos.capture(move))
			return move;
		/* fallthrough */

	case KILLERS:
		++stage;
		move = killers[1]; // Second killer move
		if (move != MOVE_NONE
			&&  move != ttMove
			&&  pos.pseudo_legal(move)
			&& !pos.capture(move))
			return move;
		/* fallthrough */

	case COUNTERMOVE:
		++stage;
		move = countermove;
		if (move != MOVE_NONE
			&&  move != ttMove
			&&  move != killers[0]
			&& move != killers[1]
			&& pos.pseudo_legal(move)
			&& !pos.capture(move))
			return move;
		/* fallthrough */

	case QUIET_INIT:
		cur = endBadCaptures;
		endMoves = generate<QUIETS>(pos, cur);
		score<QUIETS>();
		partial_insertion_sort(cur, endMoves, -4000 * depth / ONE_PLY);
		++stage;
		/* fallthrough */

	case QUIET:
		while (cur < endMoves
			&& (!skipQuiets || cur->value >= VALUE_ZERO))
		{
			move = *cur++;

			if (move != ttMove
				&& move != killers[0]
				&& move != killers[1]
				&& move != countermove)
				return move;
		}
		++stage;
		cur = moves; // Point to beginning of bad captures
					 /* fallthrough */

	case BAD_CAPTURES:
		if (cur < endBadCaptures)
			return *cur++;
		break;

	case EVASIONS_INIT:
		cur = moves;
		endMoves = generate<EVASIONS>(pos, cur);
		score<EVASIONS>();
		++stage;
		/* fallthrough */

	case ALL_EVASIONS:
		while (cur < endMoves)
		{
			move = pick_best(cur++, endMoves);
			if (move != ttMove)
				return move;
		}
		break;

	case PROBCUT_INIT:
		cur = moves;
		endMoves = generate<CAPTURES>(pos, cur);
		score<CAPTURES>();
		++stage;
		/* fallthrough */

	case PROBCUT_CAPTURES:
		while (cur < endMoves)
		{
			move = pick_best(cur++, endMoves);
			if (move != ttMove
				&& pos.see_ge(move, threshold))
				return move;
		}
		break;

	case QCAPTURES_1_INIT: case QCAPTURES_2_INIT:
		cur = moves;
		endMoves = generate<CAPTURES>(pos, cur);
		score<CAPTURES>();
		++stage;
		/* fallthrough */

	case QCAPTURES_1: case QCAPTURES_2:
		while (cur < endMoves)
		{
			move = pick_best(cur++, endMoves);
			if (move != ttMove)
				return move;
		}
		if (stage == QCAPTURES_2)
			break;
		cur = moves;
		endMoves = generate<QUIET_CHECKS>(pos, cur);
		++stage;
		/* fallthrough */

	case QCHECKS:
		while (cur < endMoves)
		{
			move = cur++->move;
			if (move != ttMove)
				return move;
		}
		break;

	case QSEARCH_RECAPTURES:
		cur = moves;
		endMoves = generate<CAPTURES>(pos, cur);
		score<CAPTURES>();
		++stage;
		/* fallthrough */

	case QRECAPTURES:
		while (cur < endMoves)
		{
			move = pick_best(cur++, endMoves);
			if (to_sq(move) == recaptureSquare)
				return move;
		}
		break;

	default:
		assert(false);
	}

	return MOVE_NONE;
}




